1. Field of the Invention
The present invention relates to a band gap reference-type reference voltage generation circuit for use in portable systems, battery-powered systems, integrated circuits provided therein, etc.
2. Description of the Background Art
A reference voltage generation circuit including a band gap reference circuit (referred also as a “BGR circuit”) is typically used in various analog circuits provided in semiconductor devices in order to suppress variations in the overall characteristics of the circuits due to variations in the power supply voltage and the temperature. A reference voltage obtained by means of such a BGR-type reference voltage generation circuit is known to be little dependent on the power supply voltage or the temperature.
An example of a known reference voltage generation circuit including a BGR-type reference voltage generation circuit is the reference voltage generation circuit shown in FIG. 5 of Japanese Laid-Open Patent Publication No. 10-198447 (Patent Document 1). The reference voltage generation circuit includes PMOS transistors P1, P2 and P3, NMOS transistors N1 and N2, a diode D1, and resistors R1 and R2. In the reference voltage generation circuit having such a configuration, a current according to the gate-source voltage of the NMOS transistors N1 and N2 flows through the first current path including the PMOS transistor P1, the second current path including the PMOS transistor P2, and the third current path including the resistive element R2 and the diode D1.
In the paragraphs mentioned above, Patent Document 1 describes that the output voltage (reference voltage) Vref is as expressed in the expression below, where the PMOS transistors P1, P2 and P3 are of the same transistor size, and the transistor size ratio between the NMOS transistors N1 and N2 is 1:M.
      V    ref    =                    N        ·                  (                      k            ·                          T              q                                )                ·        ln            ⁢                          ⁢      M        +          VF      ⁡              (                  D          ⁢                                          ⁢          1                )            
In the expression, N denotes (Resistance value of R2)/(Resistance value of R1), q the charge of electron, k the Boltzmann constant, T the absolute temperature, VF(D1) the forward voltage of D1.